Windows Server 2008 R2 DNS lookup failure

I have two DC's, one is WinServ 2008 R2 Standard and one is WinServ R2 Enterprise. On the Enterprise server i get a lot of errors regaring the DNS. Browsing to the Server Manager -> Roles to the DNS part i get the error "The server X could not be contacted. The error was: Access was denied. Would you like to add it anyway?" If i go on Yes, i will have the server displayed in the DNS area with the forbidden sign. On the Standard DC the DNS is working but it seems to me that the two DC's cannot see eachother also.
Looking at the errors from the DNS log, i can read a lot of Event 4000 errors: "The DNS server was unable to open Active Directory".
I can't figure out what is the problem and where to look for a fix... please help.

it seems that the DNS and AD connection was lost between the two servers (both shutdown in the same time - power loss). After leaving them over the weekend the sync between the servers and AD+DNS was up again. Now it's working.

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